The present invention relates to a scroll fluid machine comprising compressing and expanding sections and especially to a scroll fluid machine used to feed air into and discharge it from a fuel cell.
In a fuel cell, there is electrolyte between an anode and a cathode, and hydrogen is fed as cathode active material to the cathode. Hydrogen from which electrons are taken away at the cathode becomes hydrogen ions which move to the anode through the electrolyte. Oxygen is fed as anode active material to the anode and receives electrons from the cathode through an external circuit to allow the hydrogen ions to react with oxygen to form water. Hence electrons flow from the cathode to the anode or an electric current flows from the anode to the cathode. Generally oxygen-containing air is fed to the anode, so that unreactive oxygen and nitrogen as main component of air exist on the anode in addition to water.
Combination of hydrogen and oxygen is exothermic reaction and its temperature rises from supplied air. The gas which contains nitrogen as main component should be discharged from the anode.
Air pressurized by a compressor is fed to the anode, and the gas at the anode has higher pressure than atmospheric pressure. If the gas is released to air, it will become loss without doing work. Energy of the gas is retrieved through an expander. Thus, the fuel cell may preferably have a compressor and an expander.
U.S. Pat. No. 6,506,512 BI to Mon et al. discloses a compression regenerative machine for a fuel cell as fluid machine having a compressor and an expander. The scroll fluid machine has an orbiting scroll each side of which has a scroll wrap, one scroll wrap compressing sucked fluid, while the other expands sucked fluid to do work.
In the compression regenerating machine, fluid expanded and fallen in temperature in an expanding section cools an orbiting scroll from the expanding section, and fluid is expanded from the center to the circumference. However, there is no expanded or cooled fluid at the center, and no consideration is paid on cooling a bearing for an eccentric pin, a journal bearing for a driving shaft at the center of the orbiting scroll or an electric motor for driving a driving shaft.
Thus, in a small space such as an automobile engine room isolated from outside, surrounding temperature rises to lead poor heat radiation for a long time operation to raise temperature of the bearing thereby decreasing it life. Thermal expansion results in contacting the stationary scroll with the orbiting scroll to damage them. The electric motor heated during rotation for the driving shaft decreases its life.
In view of the foregoing disadvantages, it is an object to provide a scroll fluid machine having a compressing section and an expanding section at both sides of an orbiting scroll end plate, fluid which is fallen in temperature with expansion in the expanding section being applied to cool an orbiting scroll, a bearing or a driving machine effectively.
The foregoing and other features and advantages of the invention will become more apparent from the following description with respect to embodiments as shown in appended drawings.